Byrd has orchestrated and witnessed maneuvering. He has presided over the shortest session in Senate history -- not even one second long -- and presided for the longest continuous period -- more than 21 hours. He has thundered from the Senate well with rhetorical flourish.

And when success has hinged on just showing up and voting, he has done so.

This week, amid a historic blizzard, the 92-year-old senator arrived in the wee hours after midnight, and in the frigid minutes just after dawn. When an aide guided him in his wheelchair onto the chamber floor just after 7:30 a.m. Tuesday, his fellow Democrats leapt to their feet and cheered, for the third time in five days.

Their decades-long quest to reform the nation's health-care system was within reach, with 60 votes finally in hand after a weekend compromise, so long as every single Democrat voted. Byrd seemed to relish his contribution.

On Tuesday, he spent 25 minutes on the floor, making spirited small talk with fellow senators, including Thad Cochran (R-Miss.). He shouted "Aye" each time his name was called, then left the chamber to handshakes and backslaps.

Sen. Christopher J. Dodd (D-Conn.), who sits next to Byrd in the chamber, took note of his cheery attitude this week. "He looks a lot better, he seems a lot better, than a few weeks ago," Dodd said. He added that Byrd is "clearly aware" of who his colleagues are, their families and their legislative interests.

This week, Byrd has talked to senators about intricacies of northern border issues and to administration officials about America's energy needs. On Monday, in addition to rolling into the Senate chamber at 1 a.m. to vote, his wheelchair leaving streaks of slush in the hallways, he did some business on behalf of West Virginians. He met with Environmental Protection Agency chief Lisa Jackson, at her request, in his offices, to continue talks on parameters for mining permits.

But Byrd's fragile health has caused him to miss more than 40 percent of the chamber's roll calls this year. And as the debate has grown more heated, Byrd's appearances have become a flashpoint in a legislative fight split precisely on party lines.

Democrats accused Republicans of mistreating the longest-serving member of Congress in history by forcing 60-vote hurdles at awkward times that left even the most robust senators grumbling. Republicans remained unapologetic that Byrd has been forced into dark-of-night and predawn votes, alleging a Democratic rush to approve health care is forcing the nonagenarian into precarious votes.

"I've been worried about Senator Byrd living through the physical trauma of the past few weeks. It is an inevitable thought when you see him rolled into the chamber at 1 a.m.," said Sen. Arlen Specter (D-Pa.), who has served for 29 years with Byrd. "Compelling Senator Byrd to vote needlessly is a new Senate low mark."